1. Technical Field
The present invention relates to a technique for detecting, for example, a tip of a robot arm by ultrasonic waves, and relates to a technique in which detection error due to the effects of sonic speed is reduced.
2. Background Art
A technique in which the three-dimensional position of an object is detected by using ultrasonic waves is known (See Reference 1 below). In this technique, for example, an ultrasonic wave generating device is arranged at a part to be detected (detection target), and ultrasonic wave signals generated therefrom are received at three distinguishably different points. At that time, by measuring the time required for the ultrasonic waves to move through the air at the three points, distances r1 to r3 from the three points to the detection target can be calculated. By describing three spheres, each having a central point of one of the three points and a radius of r1, r2, and r3, the point at which these spheres intersect can be specified as the position of the detection target.    Reference 1: Japanese Unexamined Patent Application Publication No. Heisei 06 (1994)-102350.